Diesel engines may run on biodiesel, a sustainable fuel that can be made from a variety of feedstocks using various alcohols and catalysts. The type of alcohol has a direct impact on the biodiesel’s fuel qualities. Variations in fuel qualities can lead to variations in diesel engine performance, combustion, and injection characteristics. Using blends of 10%, 20%, 30%, and 40% with Karanja oil and regular diesel fuel separately, experimental tests were conducted to assess the performance and emissions of a direct injection, water-cooled Kirloskar diesel engine at 1500 rpm with variable load. The 3-hole and 5-hole fuel injectors are the subjects of this investigation. Because Karanja methyl esters (KME) have a lower calorific value than diesel, their value increases with the proportion of KME in the mix. For a 20% blend, this means that brake-specific fuel consumption increases. As the amount of KME in the gasoline increases, the brake thermal efficiency falls. At a 20% mix, Brake thermal efficiency is almost identical to diesel fuel. For all blends, CO and HC emissions rise with load and fall with the fraction of KME in the mix. For every combination of KME, the density of smoke rises as the load increases. Smoke density falls as the fraction of mixes containing KME rises. It has been observed that when nozzle holes are increased from three to five, brake thermal efficiency rises with load. When comparing a 5-hole to a 3-hole with load, the Brake-specific fuel consumption (BSFC) will fall. Nozzles have an influence on emissions in that as nozzle holes grow, so do CO, HC, and smoke opacity. According to the findings, a 20% KME blend for a 5-hole fuel injector nozzle is a good substitute for diesel.